Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.30	7.683%	$70.317	$70.32	$70.30	$70.30
Purchase #2	$195.86	10.556%	$216.535	$216.54	$216.55	$216.50
Purchase #3	$128.29	9.274%	$140.1876	$140.19	$140.20	$140.20
Purchase #4	$20.58	12.823%	$23.219	$23.22	$23.20	$23.20
Purchase #5	$171.80	8.159%	$185.8172	$185.82	$185.80	$185.80
Purchase #6	$100.61	10.698%	$111.3733	$111.37	$111.35	$111.40
Purchase #7	$193.85	9.117%	$211.5233	$211.52	$211.50	$211.50
7 purchase totals =	$876.29		$958.9724	$958.98	$958.90	$958.90